What Hit the Earth in 1908?

On the morning of June 30, 1908 a brilliant fireball, blazed through the skies over Siberia, exploding above the Stony Tunguska River with the force of a 12-megaton bomb. The blast knocked down trees for up to 30 kms. around, set the forest ablaze and caused shockwaves like an earthquake.

Astronomers think that the Tunguska object was a fragment from the head of a comet. It was about 330 feet across and weighed a million tons, cites Hamlyn's Giant Book of Facts.

Another such object could hit the Earth at any time. If it descended over a city, it would cause massive devastation.

Severka times a year lumps of rock and metal plunge to Earth. Scientist call these meteorites, and they are debris left over from the formation of planets. Meteorites have been known to crash through the roofs of houses, and one in 1954 badly bruised a woman in Alabama, USA.

A meteorite gauged out a crater one kilometer wide in the Arizona desert. The largest known meteorites lies where it fell in prehistoric times, at the Grootfontein in Namibia, Africa. It is made of iron and nickel and estimated to weigh 60 tons.